1. Field
The present disclosure generally relates to composite structures and, in particular, to the fabrication of composite structures. Still more particularly, the present disclosure relates to a method and apparatus for fabricating thermoplastic composite parts.
2. Background
Aircraft are being designed and manufactured with greater and greater percentages of composite materials. Composite materials are used in aircraft to decrease the weight of the aircraft. This decreased weight improves performance features such as payload capacities and fuel efficiencies. Further, composite materials provide longer service life for various components in an aircraft.
Composite materials are long lasting, lightweight materials created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in polymer resin matrix. The fibers may be unidirectional or may take the form of a woven cloth or fabric. Resins used in composite materials may include thermoplastic or thermoset resins. A thermoplastic material may become soft upon heating and may harden upon cooling. A thermoplastic material may be able to be repeatedly heated and cooled. A thermoset material may become hard after being heated to a curing temperature. In thermoset composites, fibers and resins are arranged and cured to form a composite material. Thermoset materials may not become soft upon being heated again.
Numerous processes exist for the fabrication of Thermoplastic composite (TPC) laminates of constant thickness and straight length. In addition to non-continuous processes such as pressing, stamping and autoclave forming, there are continuous processes such as extrusion, pultrusion, roll forming, and compression molding. Although these latter processes are capable of producing parts in continuous lengths, they lack the ability to produce parts of varying thickness that are needed for lightweight aerospace structures and other structures where weight is of particular importance. Moreover, the processes mentioned above are not capable of producing parts that have curvature along their length.
There thus exists a need to provide a new method that is capable of fabricating curved TPC laminates with tailored thicknesses in a continuous process. Preferably, such a method should be a low cost method and take advantage of automated equipment where possible.
Further, during continuous compression molding, it may be desirable to have substantially even pressure distribution on material. Continuous compression molding applying uneven pressure distribution on material may result in less than desired quality. For example, applying uneven pressure may result in a product with non-uniform thickness, porosity, or other inconsistencies. Thus, there exists a need to provide a method and apparatus capable of providing substantially even pressure distribution to thermoplastic laminates during continuous compression molding.